Laminated container



July 25, 1961 w. B. WILKINS 2,993,634

LAMINATED CONTAINER Filed Nov. 15, 1957 'INVENTOR.

WILLIA M BURDETTE WILKINS v BY: :1 Ir IZ, M 7/} 8 ATTaRNEYS UnitedStates patent,

2,993,634. LAMINATED CONTAINER William Burdette Wilkins, Roxboro, N.C.Filed No 15, 1957, Ser. No. 696,716 3. Claims. (Cl. 229-35) containersare somewhat fragile and theoverlappingpon.

tions are objectionable for many, purposes.

It is an object of the present invention to provide a containercomprising a skeleton or shell of paperboard; which said skeleton orshell is covered or encased: inv a sheath or coating of fibrousreinforcing material impregnated with a thermosetting resin.

It is a further object of the invention to provide for forming thepaperboard skeleton or shell in such manner as to avoid overlappingportions which result in non-uniform wall thicknesses.

The invention, accordingly, is embodied in a container of a form suchthat it is adaptable to fabrication from sheets of paperboard byappropriate scoring of the surface and cutting of the corners so that itmay be folded to the contour of a box, for example, whereupon the box isthen subjected to a laminating process in which it is enveloped in alayer of fibrous material impregnated with a thermosetting resin, afterwhich it is passed to a molding stage, in which the box is placed in amold and baked to cure the resin. Thus, there is formed a box having itsbottom, sides and ends formed from paperboard laminated with a layer ofplastic impregnated fibers, the box being further characterized by thefact that. the layer of plastic impregnated fibers forms an outer sheathor coating for the paperboard skeleton and that substantially. noimpregnation of the paperboard skeleton itself with' the plasticmaterial occurs.

Reference to the drawings will illustrate the, invention in furtherdetail, wherein FIGURE 1 illustrates a layout of a corner of the box toshow an inside corner formed in accordance with a preferred example ofthe invention;

FIGURE 2 is a perspective 'view of the inside corner shown in FIGURE 1;

FIGURE 3 is an illustration of the completed box with the external resinimpregnated fibrous laminate;

FIGURE 3a shows a reinforced corner;

FIGURE 4 is a section taken along the line 44 of FIGURE 3 afterapplication of the resin impregnated fibers, but before molding;

FIGURE 5 is a similar section after molding and showing the form oflaminations in the completed box;

FIGURES 6 and 7 illustrate alternative versions of the corner structure;and

FIGURE 8 illustrates the box in section, in a heat curing apparatus.

Referring now to FIGURE 1, 10* represents the body of the box which ismade up of bottom 11, side walls 12 and 13, each of which terminates inan car 14 and 15. The bottom has an extension 16 which may be consideredthe end for purposes of this illustration. Also for purposes ofillustration, details of the description are applied only to one cornerof the box, because the others would be substantially identical.

In laying out the sheet appropriately for the bottom, the widths of theprojections 12, 13 and 16 are made the 2,993,634 Patented J uly 25, 19612- same, because when turnedzup-alongthe score lines 17-,- 18 and 19,theyfo'rmthesides and end of;the container. At each corner, for,example, inthe corner carrying the car 15, the. side flap is cut in an.outline which commences with a diagona1:line20 substantially at. 135toscoreline 18. An extension. therefrom, in this figure, iscllt asan.

arcuate section or ear. 21, which is turned back on itself at'ZZsubstantially at;45;: tolineltland-is then completed on the diagonalline 23-, which may be an extension of the 45 line or may..be.atanydesired-angle. If the box is to be made. as a straight sidedparallelepiped, the angle to be. formed by the sideflapslZ, 13.and 16withthebottom 11 is a right angle and-edge. 24,becomes an extensionofthe .edge of the flap 13-;

If it is desired tov have the box with slightly tapered side walls, anappropriate orientation of the angle of the edge 24' is made so that thecorner on theline 24 and 23 will be a continuation at the same level asthe outer edge of the flap 16. This latter is; a requirement of geometryof the box and the exact angle. atwhich line 24 is sloped is determinedby theform of cut worked into the flap for assembly of the end and the.angle at which theincision 20 approaches the scoreline '18;

To correspond to the flap 15 appropriate incisions are made in the flap16; thus ZW-matches cut 20; the outline 21" matches the ear 21; 22matches the cut 22; and 23' matches the cut 23. When. the side'isassembled, the flap 15 with the arcuate projection 21 fits against thecorresponding flap 16 to form a continuous planar side, as shown inFIGURE 2.

In laying out the corner, the exact form of cut is not critical; ratherit is important for purposes of the invention only that the contour ofthe end of flap 15 conform to and match the contour of the abutting endof flap 16.

In the form of the box shown, the planar sheet of paperboard is cut out,scored, andthe corners cut in accordance with the outline described. 'Inthe second operation of forming the box, the sideflaps are folded up andfitted together, as shown in FIGURE 2. In general the natural thicknessand rigidity of paperboard of this form is such that the box may beloosely assembled with the sides and end flaps in. proper relation. Itthen passes to the third step of formation in which fibrous materials,for example, glass fibers, which will provide tensile strength,

are wrapped in a thin layer around the bottom and all: of

the sides of the box,

. Thefi'brous m ter a s r s r 1 st -v w th? t re n e n es t f rm thabase o e l min tiquwhish will be the finished box. The product, thusassembled, is then passed to the heat treating stage, which involvesfitting it into a die -81, as shown in FIGURE 8, where it is heated to atemperature of the order of 200250 to cure the resin. With the curing,the resin and the box form a complete assembly in which the side wallsare of uniform thickness and, particularly, the ends have no projectionscaused by overlap of corner flaps. The butt joints thus formed at theends may be characterized as such and derive their strength from thepresence of the fibrous materials in the external plastic layer and theinterlocked form of flap.

For forming the external plastic layer, glass fibers are first wettedwith resinous material so that they are covered with a layer of plasticbefore being wrapped around the sides of the box. By this technique acomplete assembly with virtually no impregnation of the board isaccomplished.

FIGURES 6 and 7 illustrate other geometrical forms of cut-outs for thesides. Thus, in FIGURE 6 the side is formed by means of a strip scoredat intervals defining the dimensions of the box and having the ends cutwith straight projections and matching indentations on the V 3 other aremade for complete assembly. FIGURE 7 illustrates the addition ofdiagonal cuts.

FIGURE 3a illustrates another form of the box which is characterized byhaving the sides and ends formed of a double layer of box stock with thebutt joints in each layer being offset from each other. Thus, in FIGURE3a the parts corresponding to each of FIGURE 3 are correspondinglyidentified. An inside layer, which consists of box stock strip 50,corresponding in width to the height of the box and having, for example,a single butt joint 51 therein, is fitted into the box, joint 51 beingon the side adjacent to that in which a joint in the box side is formed.

It is apparent, of course, that if an exceptionally high strength, heavybox is needed, three, four or more layers or plies of box stock could belaminated to form the sides and ends, the butt joints in the layersbeing oriented to alternate sides of a corner. Likewise, the bottom ofthe box may, if desired, be reinforced by one or more additional layersof box stock.

When extra layers or plies are used to form the sides, ends or bottom ofthe box, the facing surfaces of adjacent plies or layers are preferablynot bonded together. This not only results in a saving in cost but alsoresults in an increase of impact strength in the finished box.

For purposes of the invention, the lamination of a plastic-wettedfibrous material may be carried out not only with glass fibers but otherfibrous materials such as cotton, rayon, nylon, sisal, or the like,which are sufficiently heat resistant to withstand molding temperaturesas high as 225 to 250 C. A similar requirement, of course, applies tothe resins and for the purposes of the invention, I prefer plastisolscomposed of polyester resins, such as those available commercially inliquid form from Rohm and Haas Co. epoxy type resins also obtainable inliquid form from the Bakelite Company, or the Shell Chemical Company,phenol formaldehyde resins, urea formaldehyde resins, etc. That is, theresin to be used may be any resin suitable for heat polymerization andsetting or any plastisol which is cured by heating to a temperature toabout 225-250" C. The characteristic form of the completed box is thatthe product is formed without material penetration of the box stockitself by the resin which forms the adhesive layer around the fibers.The

box as shown in FIGURES 4 and 5 characteristically consists of thecentral internal core 40 of box making stock, e. g., paperboard or othersimilar sheet material, and an inner layer 41 and an outer layer 42consisting essentially of fibers and the resin. No material penetrationof resin into the box stock appears. It is also to be understood thatthe fibers when used are preferably oriented across the cut which isused to form the corners.

That is, referring to FIGURES 1 and 2, one cut formed by the lines 20,21, and 23 forming the joint may be said to be approximately at a 45angle to the score line 18. The fibers forming the laminate around theside of the box are preferably oriented parallel to the score line 18 sothat such tension as is applied to the joint when the box is packed is atensile force applied to the fibers along the direction of their maximumstrength. It will also be understood that when extra layers or plies areused, as shown in FIGURE 3a, the opposed facing surfaces of the strip 50and sides 13 and ends 16, are preferably not bonded together, exceptinsofar as the wrapping of fibers and resin may cause adhesion at theedges..

It will be understood that the invention may be variously modified andembodied within the scope of the subjoined claims.

What is claimed is:

1. A unitary container formed from a fibrous sheet material to provide arelatively shallow tray having a bottom formed of a central layer ofsaid sheet material and outwardly extending sides from each of the sidesof said bottom, said fibrous material being a box forming material whichis cut from a sheet to form the said central bottom with the outwardlyextending sides integral therewith, the said sides defining the depth ofthe container, the said sides further being characterized by being ofuniform thickness throughout their full length around the container,joints connecting the said sides being formed by abutting andinterlocking edges formed in a plane, the said edges being held in fixedmatched relationship by an externally-applied, fibrous,plastic-impregnated reinforcing layer, wherein the fibers of said layerextend essentially transversely across the said abutting, interlockingjoint.

2. A container in accordance with claim 1, wherein said external fibrousmaterial is a layer of glass fibers.

'3. A container in accordance with claim 1, in which the sides arereinforced and formed of a plurality of layers of box forming material.

References Cited in the file of this patent UNITED STATES PATENTS147,710 Thomson Feb. 17, 1874 377,813 Munson Feb. 14, 1888 981,993 GairJan. 17, 1911 1,006,722 Claussen Oct. 24, 1911 1,303,687 Lefller May 13,1919 2,341,845 Mark Feb. 15, 1944 2,751,109 Moore June 19, 19562,777,626 French Jan. 15, 1957

